1. Field of the Invention
This invention relates to an image reading apparatus having an image reading unit for reading information from a document medium on which images are formed and a control unit for executing processing for controlling the image reading unit.
2. Description of Related Art
Conventionally, an image reading apparatus reads a document through reading glass while conveying the document with a reading unit secured at a document reading position. With such a reading unit, where a foreign material, such as, e.g., debris or dust, attaches to the reading unit, the foreign material is reproduced as a vertical streak on a read image. Therefore, for example, as described in Japanese Unexamined Patent Publication No. 2005-5957, such an image reading apparatus has an openable shutter on an upper surface of the reading glass to prevent foreign materials from attaching to the reading glass by rendering the shutter open at the time of reading.
Such a conventional image reading apparatus, however, raises a problem that the reading time becomes long where successively reading document media of plural sheets as preventing foreign materials from attaching to the reading unit because rendering the shutter open and closed at each reading time of the document media.
This invention is made in consideration of the above described problem, and it is an object of this invention to provide an image reading apparatus capable of shortening a document reading time where successively reading a plurality of the document media while preventing foreign materials from attaching to the reading unit.